Apparatuses for the treatment of fluids, such as automatic apparatuses for analysis or reactions using chemical products, are known. These known apparatuses frequently have drawbacks. Thus, in the known analysis apparatuses, the mixing of the sample to be analyzed with the reagent or reagents generally takes place in an atmospheric medium. Moreover, said known apparatuses commonly need distinct means for taking the sample to be analyzed, for distributing the reagent or reagents, and for diluting and conveying the obtained mixture or solution to the detection or treatment device.